A thorough study by Keller and Zumino of the properties of (REF ) has shown that a unique potential function can only be obtained from \(B_2(T)\)  if the potential behaves monotonically [1]}. This is clearly not the case for the Lennard-Jones potential and all its variants. As a result, there exists an ambiguity in the choice of the microscopic potential, leading to the same thermodynamic function \(B_2(T)\) . In addition to this analytic inexactness there is also the limited range of measurements of \(B_2(T)\)  for low temperatures. The aforementioned limitations lead to several possibilities of choice for \(v(r)\) , at least from measurements of \(B_2\) , specially for the power of the repulsive term \(B/r^{ \delta }\) . The possibilities range from \(n=9\)  to \(n=14\)  since the early works of Lennard-Jones (see [2]}, [3]}) and De Boer (see [4]}). We come back to this point in the next section, giving some hints about the applicability of the \(10-6\)  potential for low temperatures.
